Multiple-amplifier arrangement



June 10, 1930. BELUN] MULTIPLE AMPLIFIER ARRANGEMENT Filed Jan. 12, 1927INVENTOR ETTORE 8ELL|NI BY W AT ORNEY Patented June It), l'llivll UNITEDSTATES ETTORE BELLINI, F PARIS, FRANCE I MULTIPLE-AMPLIFIER ARRANGEMENTApplication filed January 12, 1927, Serial No. 160,555, and in FranceFebruary 2, 1926.

The present invention relates to multigroup amplifier tubes adapted tobe substituted or interchanged one for another.

To make amplifiers capable of working at high efficiency over a verywide range of wave-lengths, it has been suggested to arrange between theinput and the output terminals of the apparatus, several amplifierscomprising independent tubes, and each in tended to insure operation ofthe apparatus inside a range or scale forming part of the field ofapplication of the apparatus.

The substitution of one amplifier group for another according to thereception dealt with is insured by means of change-over switches. Aswitch disposed between the input terminals of the apparatus and theinput terminals of each of the groups allows of uniting the group thathas been chosen with the input terminals of the apparatus. An-

other switch arranged in a similar way so as to connect the outputterminals of the apparatus with the output terminals of the particulargroup that is operative.

Now, these switches constitute an element of complication in circuitarrangements, making for higher cost of manufacture, but the mostserious drawback is that these switches, especially the one at the inputend,

i tend to introduce stray capacitance that is harmful so far astheoperation of the apparatus at very high frequencies is con cerned.

Now, the present invention obviates the said accessory parts and allowsof a simplification of the connections. The features of the inventiontogether with the objects and advantages thereof will best be understoodby reference to the following description taken in connection with theaccompanying drawing in which the single figure shows a circuitarrangement whereby either of two amplifier groups may be employed.

The desired result may be realized in the following manner To one andthe same input terminal a of the apparatus there is connected the gridof the first tubeof each of the groups or banks of selective orreplaceable amplifiers, 1 and 2. The tuned input circuit b has itsinductance coil grounded substantially at its mid-point, the jointheating-currentsource A also being grounded. Furthermore, to one and thesame output terminal c of the apparatus there is connected the plate ofthe last tube of each of the said groups, the other terminal cl beingunited with the common plate-current source B.

The change-over from one group or bank to another is then obtained andeffected automatically by the starting of the filaments of the group tobe put in service.

Having thus described my invention, I claim:

1. A radio receiving arrangement for use over a comparatively wide rangeof wavelengths, comprising a common radio frequency input circuitcapable of being tuned over the entire wave-length range, a common audiofrequency output circuit, a plurality of independent groups ofcascade-connected tube amplifiers arranged .to operate within differentbands ofsaid range and connected between said common input and outputcircuits, and means for selectively rendering operative one of saidamplifier groups by closing the filament heating-circuit of that group.

2. A radio receiving arrangement for use over a comparatively wide rangeof wavelengths, comprising a common radio frequency input circuit havingits inductance grounded at its midpoint and capable of being tuned overthe entire wave-length range, a common audio frequency output circuit, aplurality of independent groups of cascade-connected tube amplifiersarranged to operate within different bands of said range and connectedbetween said common input and output circuits, a grounded filamentheating-circuit for said amplifier groups, and means for selectivelyrendering operative one of said amplifier groups by closing the filamentheating-circuit for that group.

3. A radio receiving arrangement for use over a comparatlvely wlde rangeof Wave.

lengths, comprising several independent groups of cascade-connected tubeamplifiers, each group arranged to operate within a dif ferent band ofthe entire Wavelength range,

the grid of the first tube in each group being;

connected to a common radio frequency input terminal, and the plate ofeach tube being connected to a common plate-current supply, except thelast tube in each group which are connected together to one 7 terminalof the audio frequency output, and means for selectivelyroperating anyone' of said amplifier groups.

4. A radio receiving arrangement for use over a comparatively wide rangeof wavelengths, comprising a common radio frequency input circuitcapable;;of being tuned to Wave-lengths Within said range, a pluralityof independent groups of cascade connected Y tube amplifiers, each grouparranged to operate Within a different band ofthe entire wavelengthrange, the grid of the first tube in each group being connectedtoa'common terminal of said input circuit,and the plate of each tube,except the last tube in each group, being connected to a commonplate-current supply, and means for selectively operating I any one ofsaid amplifier groups.

5. A radio receiving arrangement for use over a comparativelyWide'rang'e of wavelengths, comprising a common radio frequency inputcircuit capable of being tuned to wave-lengths within said range, aplurality of independent groups of cascade-Connected high frequency,detector and low-Irequency amplifier tubes, the grid ofthe' firsthigh-frequency amplifier tube in each group a being connected to acommon terminal of said input circuit, and the plates of the amplifiertubes, except the last tube ineach group, be-

ingconnected to a common plate current sup- P y, and means forselectively rendering operative the desired amplifier group. p

6. A receiving circuit for use over a comparatively Wide range of wavelengths, comprising a common input circuit capable "of being tuned overtheentire Wave length f range, said input circuit being grounded, a

common output circuit, a (plurality of independent groups. of ,cas'cae-con'nected tube amplifiers arranged tooperate with difie'rent bands ofsaid wave length range and connected between said common input and output circuits, a grounded filament heating- -circuit for said amplifiergroups, and'means associated with said-heating-circuit for selectivelyrendering'operative only one of said amplifier groups.

, ETTORE BELLINI.

